Influence of sprouting on the bioaccessibility and bioactivity of benzoxazinoids, phenolic acids, and flavonoids of soft and hard wheat cultivars

Abstract

Grain germination increases the contents of benzoxazinoids and the antioxidant capacity of wheat and differentially affects the phytochemical composition of hard and soft wheat cultivars. It was investigated whether wheat cultivars (sprouted or not) with distinct grain texture characteristics (BRS Guaraim, soft vs. BRS Marcante, hard texture) would have different behavior in relation to changes in phytochemical compounds, bioaccessibility and antioxidant capacity during simulated gastrointestinal digestion of a tabbouleh preparation. Sprouting increased the nominal amount of phytochemicals in tabbouleh resulting in increased release of phenolic acids (up to 7.5-fold) and benzoxazinoids (up to 12.5-fold) during all digestion phases besides higher bioaccessibility (up to 2.8-fold). Sprouting caused greater increase in the bioaccessibility of phenolic acids for the soft wheat cultivar (4.5-fold) than for the hard cultivar (1.9-fold) and it increased the colon available index of phenolic acids only for the soft cultivar (1.8-fold). Flavonoids, mainly represented by apigenin glycosides, were marginally increased after sprouting but underwent relative increase along digestion being the major phytochemicals found in the bioaccessible fraction obtained after intestinal digestion (73–94% of total phytochemicals). The increase in apigenin glycosides was associated to the increase of in vitro and intracellular antioxidant capacity of tabbouleh along digestion. Sprouting increased the peroxyl radical removal capacity of tabbouleh in the gastric phase and in the non-bioaccessible fraction regardless of the cultivar. The highest hydroxyl radical removal capacities were found in non-sprouted cultivars, especially in the soft texture cultivar in the undigested and bioaccessible fractions. The bioaccessible fraction obtained after wheat digestion was more efficient to scavenge intracellular ROS than undigested samples, the highest scavenging potency being observed for the hard texture cultivar with no effect of sprouting. These findings confirm the hypothesis that the phytochemicals of hard and soft wheat cultivars (sprouted or not) have different behavior during digestion in terms of biotransformation, bioaccessibility and ability to remove reactive species and indicate that tabbouleh produced from sprouted wheat results in increased release of bioactive phytochemicals during digestion.